Computer models of mathematical data, such as budgets, are usually done using a spreadsheet application that processes and performs calculations on the data entered by the user. For example, a computer model of a school's budget might show that the school will run out of money before the end of the term if it hires an extra teacher.
Most people use excel to do their spreadsheets. You can find excel in- start, programmes, microsoft office, excel.

How spreadsheets work

A spreadsheet appears as a grid, each row has its own number and each column its own letter. This labelling of rows and columns is used to give each cell a cell address or reference, for example, C5 means column C, row 5.
It is also possible to refer to a range of cells collectively, ie E4:E12 includes E4, E12 and all of the cells in-between.
Cells can contain numbers, text or formulae.

Example spreadsheet

A grocer uses a mobile shop to sell groceries to customers who live out of town. He uses a spreadsheet to keep a record of his daily sales:

Daily sales

	A	B	C	D	E
3	Produce	Unit	Number sold	Price	Sales
4	Apples	kg	7	£0.70	£4.90
5	Potatoes	25kg	8	£6.00	£48.00
6	Oranges	kg	6	£0.90	£5.40
7	Carrots	25kg	8	£8.50	£68.00
8	Sprouts	kg	4	£1.40	£5.60
9	Cabbage	kg	6	£0.70	£4.20
10	Onions	kg	9	£0.56	£5.04
11
12				Total	£141.14

There are a number of formulae in the above spreadsheet but they're hidden, only the results are displayed.